The ritual of Birkat Hachamah, blessing the sun, is recited only once every 28
years! It was last recited on April 8, 2009 and will next be recited on April
8, 2037. However, this same blessing is also recited upon seeing or
experiencing any natural phenomenon that inspires a sense of awe, such as an
earthquake, a comet, lightning, or unusually large mountains or rivers.

For Birkat Hachamah, this blessing is recited on the morning of April 8, upon
seeing the sun for the first time after it has fully risen (the entire circle
is visible above the horizon). It is best recited with a group of people,
including men, women and children.